To be fair, nigger is a slur intended for and widely used against all blacks for being black. So you using it in your own unique way doesn't eliminate the harm your use does in promoting racial bigotry. Redneck was not coined nor is it used to refer to whites generally for being white. Its meaning is to refer to people who say, do, and think (or not think) various things, with their whiteness just signalling a sub-group of people with those qualities.
The centrality of race to the basis for the slur matters.
This relates to the OP in that if race is tangential and minimal in the basis for the negative connotation, then the core meaning of the concept can and does apply to other groups, and since being Muslim refers to many of the same intolerant anti-intellectualism that defines the Islamic religion, then it might be meaningful and apt to draw an analogy that Muslims are the rednecks of the Arabic world.